Medical endoscopes are commonly used with a video camera. The video camera can be pushed onto the ocular of a conventional endoscope or incorporated into the endoscope. Endoscopes that incorporate a video camera are becoming increasingly widespread since operators want to work with a monitor, as opposed to the prior practice of working with an eye on the endoscope in an uncomfortable crouched position.
The absolute sterility of medical endoscopes before commencement of an operation has the highest priority. For instance, a very high degree of sterility is required with intra-arterial use. With the current state of the art the desired degree of sterility can only be achieved with hot steam sterilization in an autoclave. The endoscope is thus subjected to hot steam at high temperatures and pressures. The steam passes through the smallest links in the endoscope and condenses there on subsequent cooling. Drops of condensate and condensation are particularly disruptive on surfaces of lenses where they can critically impair the image quality.
Endoscopes of the type referred to above that have a rod lens image guide with a plurality of rod lenses and a large number of lens surfaces are particularly at risk to penetrating steam. In an endoscope of the type referred to above, the rod lens image guide is thus accommodated in a separate inner metallic housing with, for example, end windows soldered in a totally gas-tight manner in order to maintain the lens surfaces free of condensation, even with frequent autoclaving.
The outer housing surrounds the inner housing. A light guide fiber bundle, which is necessary for illuminating the field of view, is disposed next to the inner housing. Light guiding fibers are very difficult to seal since they are generally exposed at their ends with adhesive. The interior of the outer housing may, therefore, not be maintained free of condensation.
If a video camera is provided on such a device, either attached to the outer housing or incorporated in the outer housing, the entry window of the camera and the exit window of the rod lens optical system, which is disposed in the interior of the outer housing, also mist up.
It is the object of the present invention to construct an endoscope of the type referred to above with an optical path to the camera which is free of condensation.
In accordance with the invention, the camera is disposed within the inner housing. The camera is mounted in the inner housing in a completely vapor-sealed manner so that condensation can be reliably prevented.
The camera, which is arranged proximate to the rod lens image guide, must be disposed at a suitable focusing distance with respect to the rod lens image guide. The distance between the camera and the rod lens image guide should be adjustable, particularly in order to be able to compensate for subsequent changes of the spacing. Such spacing changes may result from tremors or thermal changes in the length of the inner housing. An adjustment device for changing the position of the camera within a vapor-tight housing, however, causes considerable sealing problems if, for example, sliding bushes or the like are used.
In further accordance with the present invention, the camera is secured to the proximal end member of a metal bellows, which constitutes a proximal end region of the inner housing. An adjustment device for changing the position of the camera engages the proximal end region of the bellows and moves the bellows relative to the distal portion of the inner housing accommodating the rod lens image guide. A focusing possibility or means for the camera is thus provided without an adjustment device having to pass through the vapor-tight inner housing.